Recently, as the demand for portable electronic products such as notebooks, video cameras, mobile phones, etc. are rapidly increasing, so are the development of energy storage batteries, robots, satellites, etc., which is leading to the extensive research on high-performance secondary batteries capable of repeated charge and discharge.
Commercially available secondary batteries at present include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium secondary batteries, etc. Among them, the lithium secondary batteries are less susceptible to memory effect compared to nickel-based secondary batteries and thus can be freely charged and discharged. Moreover, the lithium secondary batteries are attracting much attention for its very low self-discharge rate and high energy density.
In particular, with the recent increase in the interest in the environment where carbon energy is being depleted, environmentally-friendly vehicles such as hybrid vehicles, electric vehicles, etc. have attracted much attention all over the world, including USA, Europe, Japan, and Korea. In such a hybrid vehicle or electric vehicle, the most critical component is a battery, for it provides a driving force to a vehicle motor. The hybrid vehicle or electric vehicle are powered by the charge and discharge of the battery, and thus have high fuel efficiency and do not emit pollutants compared to conventional vehicles powered by internal combustion engines. As a result, the number of users of such vehicles is significantly increasing.
In the case of the battery that is used in such a hybrid vehicle or electric vehicle, the battery's state-of-charge (SOC) may be reduced to the lower limit during operation of the vehicle, by the natural consumption of the battery, or by a power leakage from the vehicle during stopping of the vehicle. The battery's state-of-charge reduced to the lower limit refers to a fully discharged state. At this time, no power is supplied from the battery, and thus the operation of the electric vehicle or devices powered by the battery is severely limited.
Under normal circumstances, when the battery is fully discharged or approaches the fully discharged state, the battery is charged in a battery charging station or by using a battery charger. However, when the vehicle battery is in the fully discharged state in a situation where the vehicle is not located in the battery charging station, the vehicle will not operate, making it necessary to provide emergency charging to the battery. In such a situation, the emergency charging may be provided by an emergency vehicle or another vehicle, otherwise, an emergency battery may be used instead of the fully discharged battery to move to the station.
As such, a vehicle battery provided with an auxiliary charging terminal to have an emergency charging function, a vehicle battery provided with a space for mounting an auxiliary battery, etc. have been developed to prepare for emergencies. Furthermore, a battery with both the emergency charging function and the auxiliary battery mounting function can be a very useful unit for responding to emergencies.
However, in the case of the battery with both the emergency charging function and the auxiliary battery mounting function, there is a lack of research on how to control the battery for each situation. Moreover, vehicle batteries of recent years are provided with a complex control system and various safety units. Therefore, when the emergency charging function and the auxiliary battery mounting function are simply added to the battery, a battery control apparat8s cannot effectively control the battery, and thus the battery itself may have serious safety problems.